Real World Concepts in Cloud

Understanding theory is useful, but the real value comes from knowing how things work in real applications. In this section, you will learn how a web app runs on cloud and the basic 3 tier architecture used in most systems.

1. How a Web App Runs on Cloud

Let us understand step by step what happens when a user opens a website.

Step 1: User enters a domain name

• A user types a website name like example.com in the browser.

Step 2: DNS converts domain to IP

• The domain name is converted into an IP address using DNS so the browser knows where to send the request.

Step 3: Request goes to server

• The request is sent over the internet to a server running in the cloud.

Step 4: Load balancer distributes traffic

• If the application is large, a load balancer distributes the request to one of many servers.

Step 5: Backend processes the request

• The backend application processes the request and may interact with a database.

Step 6: Database returns data

• The database sends the required data back to the backend.

Step 7: Response sent to user

• The backend sends the response back to the browser, and the user sees the result.

Example in real life:

• If you open a wallpaper website
• The frontend loads images and UI
• The backend handles search requests
• The database stores image data

2. Basic 3 Tier Architecture

Most web applications follow a 3 tier architecture. This divides the system into three main parts.

• Frontend
• Backend
• Database

1. Frontend

The frontend is what users see and interact with

It includes:

• HTML
• CSS
• JavaScript

Example:

• A webpage showing images, buttons, and search bar

Role:

• Displays data to users
• Sends requests to backend

2. Backend

The backend is the logic part of the application.

It handles:

• Business logic
• APIs
• Authentication
• Processing requests

Example:

• A Node.js server handling search queries and returning results

Role:

• Processes user requests
• Communicates with database

3. Database

The database stores all the data of the application.

• It can store
• User data
• Images
• Application data

Examples:

• MongoDB
• MySQL

Role:

• Stores and retrieves data

3. How 3 Tier Architecture Works Together

• Step 1: User interacts with frontend
• Step 2: Frontend sends request to backend
• Step 3: Backend processes request
• Step 4: Backend queries database
• Step 5: Database returns data
• Step 6: Backend sends response
• Step 7: Frontend displays result

4. Why 3 Tier Architecture is Important

Separation of concerns:

• Each part has a clear role

Scalability:

• You can scale frontend, backend, or database separately

Maintainability:

• Easy to update and manage

Security:

• Database is not directly exposed to users

5. Simple Example

Imagine a shopping website:

• Frontend shows products
• Backend handles orders and payments
• Database stores product and user data

When a user searches for a product:

• Frontend sends request
• Backend processes it
• Database returns matching products
• Frontend displays results

A web app in cloud works through a flow of request and response

• DNS helps find the server
• Backend processes logic
• Database stores data

3 tier architecture divides the system into

• Frontend user interface
• Backend logic
• Database storage

This is the foundation of almost every modern web application and is very important to understand before moving to advanced cloud topics.